The recent advances of medicine involving the use of implanted electrical devices has more and more frequently required the use of electrodes and the like, which must have extreme resistance to fractures caused by flexing. Such electrodes must have the combination of high conductivity, high flexibility, biological inertness, as well as being resistant to flex fractures. For example, in the case of a cardiac electrode, it has recently been proposed to use an extremely fine titanium or platinum mesh, which provides very good electrical properties while being able to conform itself to the shape of the heart. Additionally, when using electrodes which are placed directly on the heart, it is a requirement that the electrical conductors, which are connected to the electrodes, also be extremely flexible and resistant to fracture from repeated flexion. This is so because the heart undergoes continuous movement, which cannot be inhibited or interfered with by inflexible wires or the like. Furthermore, any fracture would adversely affect the operation of the conductor. Accordingly, it is proposed to utilize electrical conductors which are especially suited for use with implanted medical-electronic devices. More specifically, such electrical conductors could be formed of stranded wire generally having at least seven strands. The central strand is comprised of a polyester yarn, about which are wound six conductive metallic strands. The conductive strands are in turn comprised of a core of polyester yarn and have a thin silver ribbon wound thereabout. The silver ribbon could have the dimensions of approximately 1 by 13 mils.
Although the use of such highly flexible electrical conductors should be quite satisfactory as far as mechanical stress is concerned, the use of such stranded wire formed of the highly-flexible, but thin, silver ribbons presents a problem in achieving good electrical connections which also have high mechanical strength. This problem is made even more acute when the electrode is formed, not of a solid metallic plate or the like, but of an extremely fine metallic mesh or screen.
Previous attempts at forming a sound electrical connection have been centered around directly welding or silver soldering the flexible electrical conductors to the actual electrode surface. Such joining techniques would be destructive or unstable if applied to a multistranded silver ribbon-conductive mesh crimp joint.